1. extend, swell, enlarge. See increase, Expand,dilate,distend,inflate imply becoming larger and filling more space. To expand is to spread out, usually in every direction: to expand one's chest.To dilate is especially to increase the width or circumference, and applies to space enclosed within confines or to hollow bodies: to dilate the pupils of the eyes.To distend is to stretch, often beyond the point of natural expansion: to distend an artery.To inflate is to blow out or swell a hollow body with air or gas: to inflate a balloon.